Diaphragm type fluid seal

ABSTRACT

A diaphragm-type fluid seal adapted for use with a push rod exposed to pressurized air and liquid fluids. A flexible diaphragm fixedly mounted at its radially outermost portion is provided with a central opening through which the push rod extends providing frictional engagement and thus a fluid seal between contacting surfaces of the diaphragm and rod thereby isolating the pressurized air and liquid. The diaphragm is flexible to the extent of axial movement of the rod to avoid relative movement between the diaphragm and rod in response to rod movement. An adjustable member threadedly carried by the rod and engageable with the centermost portion of the diaphragm provides a way of easily and accurately positioning the diaphragm relative to the rod to eliminate undesirable spring rate effect of the diaphragm on the rod.

United States Patent n 1 Haase et al.

[ 1 Jan. 2, 1973 [54] DIAPHRAGM TYPE FLUID SEAL [73] Assignee: TheBendix Corp., South Bend, lnd.

[52] US. Cl. ..137/495 [51] Int. Cl. ..Fl6k 31/12, Fl6k 3l/36 [58]FieldofSearch ..74/l8.l;25l/6l.2;137/495, 137/501,510

[56] References Cited UNITED STATES PATENTS 2,627,703 2/1953 Spencer..l37/50l X 3,303,852 2/1967 Miller ..74/l8.l X

Primary ExaminerHenry T. Klinksiek Attorney-Gordon H. Chenez et al.

[5 7 ABSTRACT A diaphragm-type fluid seal adapted for use with a pushrod exposed to pressurized air and liquid fluids. A flexible diaphragmfixedly mounted at its radially outermost portion is provided with acentral opening through which the push rod extends providing frictionalengagement and thus a fluid seal between contacting surfaces of thediaphragm and rod thereby isolating the pressurized air and liquid. Thediaphragm is flexible to the extent of axial movement of the rod toavoid relative movement between the diaphragm and rod in response to rodmovement. An adjustable member threadedly carried by the rod andengageable with the centermost portion of the diaphragm provides a wayof easily and accurately positioning the diaphragm relative to the rodto eliminate undesirable spring rate effect of the diaphragm on the rod.

4 Claims, 5 Drawing Figures SOURCE OF PRESSURXZED FU E L PATENTEDm 2191a3.707.985

sum 1 BF 2 SOUR OF PRESS ZED FUEL seal shown and described in U.S. Pat.No. 3,114,359issued Dec. 17, 1963, in the name of E. A. Haase and havinga common assignee.

BACKGROUND OF THE INVENTION Fluid seals of various types are required influidoperated control mechanisms particularly of the hydromechanical andhydro-pneumatic types wherein a movable actuating member is exposed totwo fluids of different pressures which fluids may be the same or oneliquid and one pneumatic. In many situations, it is necessary to providethe actuating member with a fluid seal which permits movement of theactuating member as well as maintain a seal against fluid leakage due tothe fluid pressure differential thereacross such as that shown anddescribed in the above-mentioned US. Pat. No. 3,114,359. However, suchfluid seals may not be entirely satisfactory from the standpoint offrictional drag imposed by the seal on the actuating member slidablerelative thereto which, in turn, results in wear of the seal surfacesand premature failure of the seal. Assembly and disassembly problems aredirectly related to the complexity of the seal mechanism whichcomplexity is reflected in proportionally higher manufacturing andmaintenance expense. Also, it is desired to eliminate or minimize, atleast, any extraneous force due to fluid pressure unbalance which may beexerted on the actuating member.

Furthermore, frictional drag and related forces imposed on actuatingmembers which are to be accurately and consistently displaced as afunction of relatively small control forces applied thereto have anadverse effect on the response of the actuating member and contribute toundesirable characteristics such as undue hysteresis, etc.

It is an object of the present invention to provide a flexible fluidseal having a fixed outermost portion and a relatively movable innermostportion frictionally engaged with a movable member and provided withadjustable means for varying the position of the innermost portionrelative to the actuating member.

It is another object of the present invention to provide adiaphragm-type fluid seal adapted to frictionally engage a controlmember extending therethrough and further provide adjustable means forpositioning the fluid seal relative to the control member.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a sectional view ofcontrol mechanism embodying the present invention;

FIG. 2 represents a section taken on line 22 of FIG. 1;

FIG. 3 represents a section view taken on line 3-3 of FIG. 1;

FIG. 4 represents a section view taken on line 44 of FIG. 1; and

FIG. 5 represents a view of the diaphragm-type fluid seal shown removedfrom the remaining structure of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings and,in particular, FIG. 1, numeral 20 represents a portion of a fuelmetering unit shown and described in detail in the heretofore-mentionedus. Pat. No. 3,114,359 to which reference is made for specific detailsnot necessary to fully understand the present invention. In general, theportion of the fuel metering unit shown includes a multisection casing22 having an air section 24 and a fuel section 26 separated by a wall28.

The air section 24 includes a diaphragm 30 fixedly secured at itsoutermost portion of casing 22 and separating a chamber 32 from achamber 34. Chambers 32 and 34 are vented to venturi throat air pressureP, and impact air pressure P respectively, derived from a venturi, notshown.

The fuel section 26' includes a diaphragm 36 fixedly secured at itsoutermost portion to casing 22 and separating a chamber 38 from achamber 40. Chambers 38 and 40 communicate with pressurized fuel atpressures P and P respectively, in a fuel conduit 41 supplyingpressurized fuel to chamber 38. Fuel pressures P, and P are derived fromthe upstream and downstream sides of a fuel metering value generallyindicated by 42 disposed in conduit 41 thereby representing a fuelpressure differential P, P, which, for a given fuel-metering valve 42area, determines the rate of metered fuel flow through conduit 41.

The I chamber 38 is provided with a fuel outlet defined by an annularvalve seat 43 fixedly secured in an opening 44 of casing 22 by anysuitable means such as a press fit. The opening 44, in turn, dischargesfuel to a passage 46 which feeds the fuel to an engine, not shown.

The effective flow area of the valve seat 43 is controlled by aball-type valve 48 adapted to seat thereon. The-ball valve 48 is fixedlysecured to one end of an actuating member or rod 50 and is positionedrelative to valve seat 42 in response to a force balance derived fromdiaphragms 30-and 36 as will be described. To 1 that end, the fueldiaphragm 36 is provided with backing plates -52 and 54 which areclamped against opposite sides thereof by a retaining member 56 suitablyupset or otherwise connected to provide a rigid assembly. The rod 50 isaxially aligned with diaphragm 36 and extends through retaining member56 fixedly thereto.

The air diaphragm 30 is provided with backing plates 58 and 60 clampedagainst opposite sides thereof by a retaining member 62suitably upset orotherwise connected to provide a rigid assembly.

The rod extends through an opening 64 in wall 28 separating fuel and airchambers 40 and 32, respectively, and through a central hexagonalopening 66 in retaining member 62. A diaphragm retaining member 68preferably made from a synthetic material such as the commerciallyavailable plastic sold under the trade name Delrin and manufactured bythe E. I. DuPont de Nemours and Company is provided with a radiallyoutwardly extending flange 70 and a radially inwardly extending flange72 and is fixedly secured in opening 64 by any suitable means such as apress fit. An annular recess 74 formed in flange 72 is adapted toreceive an annular lip 76 defined by the outermost portion of adiaphragm-type fluid seal 78. The lip 76 is trapped in annular recess 74by a retaining ring 80, which like retaining member 68, is made ofDelrin. The retaining member 80 is fixedly secured in position relativeto retaining member 68 as shown in FIG. 1 by suitable application ofheat to fuse the retainer members 68 and 80 together.

The flexible diaphragm 78 is preferably molded from any suitablecompound such as rubber, capable of withstanding the effects of fuel andsuitably resilient to permit flexing thereof in response to movement ofrod 50 which extends through a central opening 82 in diaphragm 78. Theopening 82 is provided with an axially extending annular lip portion 84somewhat smaller in internal diameter than rod 50 provide frictionalengagement therebetween. As shown in FIG. 5, the diaphragm is providedwith an annular wall 85 extending radially inwardly from lip 76 and anangularly extending wall 86 connecting wall 85 with lip 84.

The position of lip portion 84 relative to rod 50 may be varied forcalibration purposes by an adjustable hexagonal sleeve 87 threadedinternally as at 88 and adapted to bear against lip portion 84. The rod50 is provided with a screw thread 90 and is threadedly engaged bysleeve 87 which sleeve when turned advances axially along rod 50 to adesired position as will be described. The sleeve 87 is locked inposition rotationally by a retaining ring 92 having a hexagonal crosssectional area as shown in FIG. 2 and provided with a flange 94extending outwardly therefrom. The retaining ring 92 is adapted to slidewithout interference over sleeve 87 and into hexagonal opening 66 ofretaining member 62 to thereby fix the relative positions of sleeve 87,retaining ring 92 and retaining member 62. An annular spacing member 96,having an internal diameter large enough to permit member 96 to slidewithout interference over hexagonal sleeve 87, is adapted to abutretaining ring 92. The internal diameter of spacing member 96 isenlarged over a portion thereof to receive a washer 98. A nut 100threadedly engaged with rod 50 bears against washer 98. A compressionspring 101 interposed between retaining ring 92 and a flange 102 ofspacing member 96 tends to urge the same apart.

A compression spring 104 interposed between wall 28 and backing plate 58serves to preload diaphragm 30.

OPERATION in assembling the above-described apparatus, the retainingmember 68, diaphragm 78 and retaining ring 80 are first secured to wall28 as shown in FIG. 1. The diaphragm 30 as well as diaphragm 36 withattached ball valve 48 and rod 50 are then clamped in position betweenadjacent portions of casing 22 by suitable conventional fastening means,not shown. The diaphragm 78 slidably receives rod 50 which by virtue ofthe frictional engagement therebetween tends to stretch the diaphragm 78beyond the limit of its normal flexible range which diaphragm beingrelatively small in diameter, has relatively large spring rate effectand imposes an undesirable force load on rod 50 tending to seat ballvalve 48.

The sleeve 87 is threaded on rod 50 and adjusted to abut diaphragm 78. Apredetermined fuel pressure differential P P generated across thefuel-metering valve 41 is applied across fuel diaphragm-36 therebyloading ball valve 48 against valve seat 43 to prevent fuel flowtherethro'ugh which, in turn, causes the fuel pressure P in chamber 38to increase to pressure P thereby eliminating the P, P differentialacross diaphragm 36; The downstream side of closed ball valve 48 as wellas the free end of rod 50 may be considered as exposed to ambient oratmospheric air pressure and may be neglected as far as any forcedifferential compensation therebetween. The remaining net forceunbalance acting to hold ball valve 48 against seat 43 is derived fromthe fuel pressure P in chamber 38 acting against ball valve 48 over anarea equivalent to the flow area of valve seat 43 plus any force imposedupon rod 50 by diaphragm 78 as a result of the heretofore-mentionedstretching effect thereof minus the fuel pressure P in chamber 40 actingagainst the effective area of diaphragm 78 exposed thereto.

The mean effective area of diaphragm 78 is selected to equal the flowarea of valve seat 43 such that the opposing forces derived from fuelpressure P acting thereagainst cancel leaving only the force imposed bystretched diaphragm 78 effective in holding valve 48 against valve seat43 which may be eliminated by suitable adjustment of sleeve 87. To thatend, sleeve 87 is rotated causing the same as well as the lip portion 84bearing thereagainst to advance axially along rod 50 toward seated ballvalve 48 to eliminate the aforementioned stretched condition ofdiaphragm 78 and thus undesirable force unbalance imposed on rod 50. TheI lip portion 84 may be advanced in the above-mentioned manner until theball valve 48 starts to move away from valve seat 43 to thereby indicatea reversal of force imposed on rod 50 by diaphragm 78 following whichthe sleeve 87 may be rotated in the opposite direction as necessary tolightly seat ball valve 48. Upon completing the above-describedadjustment, the sleeve 87 is locked in position by inserting hexagonalretaining ring 92 between sleeve 86 and retaining member 62. The spacingmember 102 with spring 101 interposed between flange 102 thereof andretaining member 92 is placed in position against retainingmember 92 andsecured by washer 98 and nut 100.

The compression spring 101 and compression spring 104 correspond toconstant head and constant effort" springs shown and described in theabove-men tioned US. Pat. No. 3,1 14,359.

It will be recognized from the above-described structure of the presentapplication that applicants proposed fluid seal and adjustmentmeans-therefor is particularly adapted for use in control apparatuswhere an effective fluid seal must be utilized in a relativelyinaccessible location with control structure requiring accuratecalibration after assembly. I

We claim:

1. Control apparatus including an adjustable flexible fluid sealcomprising:

a casing defining first and second fluid pressure chambers separated bya wall having an opening therein;

a first fluid pressure responsive means in said first chamber andresponsive to a control fluid pressure differential generatedthereacross;

second fluid pressure responsive means in said second chamber andresponsive to a controlled fluid pressure differential generatedthereacross;

a control rod extending through said opening and operatively connectedto said first and second fluid pressure responsive means;

valve means operatively connected to said control rod for controllingsaid controlled fluid pressure differential as a function of saidcontrol fluid pressure differential;

an annular flexible diaphragm having a central opening through whichsaid control rod extends with an interference fit therebetween toestablish frictional engagement and a corresponding fluid seal betweensaid flexible diaphragm and said control rod;

retaining means fixedly secured to said wall for retaining the radiallyoutermost portion of said annular flexible diaphragm;

adjustable means operatively connected to said control rod and theradially innermost portion of said annular flexible diaphragm forslidably adjusting the position of said diaphragm axially relative tosaid control rod to avoid stretching of said diaphragm over apredetermined range of movement of said control rod.

2. Control apparatus as claimed in claim 1 and further including:

retaining means operatively connected to said first pressure responsivemeans and said adjustable means for fixing the position of saidadjustable means relative to said first pressure responsive means.

3. Control apparatus as claimed in claim 1 wherein:

said valve means and said flexible diaphragm are exposed to a commonfluid pressure and impose corresponding opposing forces on said controlrod;

said valve means and said flexible diaphragm are provided withequivalent effective areas exposed to said common fluid pressure wherebythe opposing forces derived therefrom are balanced.

4. Control apparatus as claimed in claim 1 wherein:

said control fluid pressure differential is derived from pressurizedair; and

said controlled fluid pressure differential is derived from apressurized liquid.

1. Control apparatus including an adjustable flexible fluid sealcomprising: a casing defining first and second fluid pressure chambersseparated by a wall having an opening therein; a first fluid pressureresponsive means in said first chamber and responsive to a control fluidpressure differential generated thereacross; second fluid pressureresponsive means in said second chamber and responsive to a controlledfluid pressure differential generated thereacross; a control rodextending through said opening and operatively connected to said firstand second fluid pressure responsive means; valve means operativelyconnected to said control rod for controlling said controlled fluidpressure differential as a function of said control fluid pressuredifferential; an annular flexible diaphragm having a central openingthrough which said control rod extends with an interference fittherebetween to establish frictional engagement and a correspondingfluid seal between said flexible diaphragm and said control rod;retaining means fixedly secured to said wall for retaining the radiallyoutermost portion of said annular flexible diaphragm; adjustable meansoperatively connected to said control rod and the radially innermostportion of said annular flexible diaphragm for slidably adjusting theposition of said diaphragm axially relative to said control rod to avoidstretching of said diaphragm over a predetermined range of movement ofsaid control rod.
 2. Control apparatus as claimed in claim 1 and furtherincluding: retaining means operatively connected to said first pressureresponsive means and said adjustable means for fixing the position ofsaid adjustable means relative to said first pressure responsive means.3. Control apparatus as claimed in claim 1 wherein: said valve means andsaid flexible diaphragm are exposed to a common fluid pressure andimpose corresponding opposing forces on said control rod; said valvemeans and said flexible diaphragm are provided with equivalent effectiveareas exposed to said common fluid pressure whereby the opposing forcesderived therefrom arE balanced.
 4. Control apparatus as claimed in claim1 wherein: said control fluid pressure differential is derived frompressurized air; and said controlled fluid pressure differential isderived from a pressurized liquid.